Steam generating apparatus

ABSTRACT

Knockdown, prefabricated, steam generating apparatus includes a convection unit or boiler, one or more radiation units forming a furnace, and an unfired pressure vessel serving as a steam drum. The boiler includes upper and lower headers connected by front and rear banks of dog leg tubes forming a unit of rectangular section adapted for transportation with such section coinciding with the right of way cross section, the boiler height lying diagonally therein, and the width of the boiler extending along the length of the right of way. The furnace includes an upper header from which extends a bank of tubes overlying the upper part of the front of the boiler, the tubes fanning out to greater spacing below the front of the boiler to form a slag screen, the bank then dividing into a front portion connecting to a front lower header and a rear portion connecting to a rear lower header. The furnace is divided into a plurality of side by side units, each adapted for transportation with its height lying along the length of the right of way. A bank of return bend tubes located interiorly of the boiler between the front and rear banks of dog leg tubes forms a preheater having a lower manifold connected to a feed water pump and an upper manifold discharging to the steam drum. Downcomers connect the steam drum to the lower headers of the furnace and boiler and risers connect the upper headers of the furnace and boiler to the steam drum.

Kearns [451' Oct. 10,1972

1541 STEAM GENERATING APPARATUS [72] inventor:

National Bank Building, Houston, Tex. 77002 22 Filed: Feb. 4, 1971 21 Appl.No.: 112,622

[52] US. Cl. ..122/235 R, 122/444 [51] Int. Cl ..F22b 21/14 [58] Field of Search ..122/235, 327, 328, 329, 331,

[56] References Cited UNITED STATES PATENTS 3,559,624 2/ 1971 Sheikh ..122/235 2,856,907 10/ 1958 Koch ..122/478 2,306,183 12/ l 942 Okan iwa 122/444 FOREIGN PATENTS 0R APPLICATIONS 1,139,457 1/ 1969 Great Britain ..122/328 Primary ExaminerKenneth W. Sprague Attorney-Murray Robinson and Ned L. Conley Michael I. Kearns, 2207 Southem e st [5 ABSTRACT Knockdown, prefabricated, steam generating apparatus includes a convection unit or boiler, one or more radiation units forming a furnace, and an unfired pressure vessel serving as a steam drum. The boiler includes upper and lower headers connected by front and rear banks of dog leg tubes forming a unit of rectangular section adapted for transportation with such section coinciding with the right of way cross section, the boiler height lying diagonally therein, and the width of the boiler extending along the length of the right of way. The furnace includes an upper header from which extends a bank of tubes overlying the upper part of the front of the boiler, the tubes fanning out to greater spacing below the front of the boiler to form a slag screen, the bank then dividing into a front portion connecting to a front lower header and a rear portion connecting to a rear lower header. The furnace is divided into a plurality of side by side units, each adapted for transportation with its height lying along the length of the right of way. A bank of return bend tubes located interiorly of the boiler between the front and rear banks of dog leg tubes forms a preheater having a lower manifold connected to a feed water pump and an upper manifold discharging to the steam drum. Downcomers connect the steam drum to the lower headers of the furnace and boiler and risers connect the upper headers of the furnace and boiler to the steam drum.

4 Claims, 7 Drawing Figures PATENTEDnm 10 I972 3.696, 794

sum 1 OF 4 INVENTOR.

ATTORNEY P'A'TE'NTEDncI 10 m2 SHEET 3 [IF 4 o o o o o o D o D O O 0 o o o c o o 0 o 0 o o o o o o o o o o o o O O O ooooooooooo oooooooooo ow OOOOOOOOOOO PATENTEDUBI 10 I972 SHEET 4 BF 4 STEAM GENERATING APPARATUS BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION This invention relates to steam generating apparatus and more particularly to railway and highway portable, knockdown, prefabricated, steam generators andsubassembliestherefor.

g 2. DESCRIPTION OF THE PRIOR ART Apparatus which is expected to be transported over a railway or highway must be of such size as to fit within the volume which can legally and actually bemoved along the right of way. Particularly limiting is the transverse cross sectional area of the right of way, i.e., the horizontal extent, of such cross-sectional area of the right of way, i.e., perpendicular to the direction of travel. The X dimension, i.e., the horizontal extent, of such cross-section, is determined by the lateral extent of the paving, or the distance between rails, plus the amount of overhang permissible, which may be determined by the width of bridges and underpasses. The Y dimension, i.e., the vertical extent of such cross section, is limited by underpasses encountered along the right of 'way. The Z dimension, i.e., the axial extent, referring to the direction of travel as the axis of the right of way, is limited only by the axial extent of the truck, trailer or flat car or, in the case of a train of such equipment, by the sharpness of the curves in the right of way.

It is known to prefabricate steam generators as a package including closely integrated fuel burning and steam generating parts which, in the larger sizes or as otherwise required, can be knocked down into components of a size to be transportable by rail or highway within the aforementioned X,Y, and Z limits of railways and highways. Such generators are not, however, designed to take maximum advantage of the available X,Y,Z right of way dimensions with respect to steam generation and water heating and circulation and at the same time minimize the number of subassemblies into which the apparatus is divided when in the knocked down condition. Furthermore, such steam generators, employ steam drums partially exposed to the products of combustion and hence subject to failure due to high temperature differential stress, such failure often resulting in violent explosions.

SUMMARY OF THE INVENTION According to the invention the steam generating apparatus is divided into two major parts, namely, a convection unit or boiler and a group of one or more radiation units which constitute the furnace. The furnace and boiler, together with an unfired pressure vessel, serving as a steam separation and storage chamber, and suitable fuel firing and feeding equipment, and other auxiliaries, make up the complete apparatus. All units are designed to make the best use of the available volume as limited by the X, Y, Z dimensions of the right of way.

The boiler includes upper and lower headers with forwardly protruding, dog leg shaped tubes extending therebetween, defining a front bank of steam generating tubes and with rearwardly protruding, dog leg shaped tubes extending therebetween defining a rear bank of steam generating tubes. The outermost rows of the two banks of dog leg tubes define a volume of generally rectangular cross section having sides'that fit within the X and Y'dimensions of the right of way, it being intended that the boiler axis defined by the plane of the headers, be tilted during transportation. The boiler axis being the diagonal of the rectangular cross section of the boiler, the distance between the upper and lower headers, i.e., the boiler height when the apparatus is in use, is a maximum within the X, Y limits of the right of way, as is desirable to achieve rapid thermosiphonic circulation, with the resultant'high steam generation capacity. At the same time the lengths of the tubes is also a maximum for non-return bend tubes, being substantially half the perimeter of the rectangular section, thereby providing maximum heat exchange surface for any given number and any given diameter of tube.

The capacity of the boiler will depend upon its width, which in transportation is the Z direction, limited only by the sharpness of the curves of the right of way.

The furnace includes an upper header overlying the top part of the front bank of dog leg tubes of the boiler. A bank of dog leg tubes extends down from the upper header parallel to the front bank of boiler tubes, and with about the same fairly close tube spacing, to the level of the bend in the front bank of the boiler tubes. Below that level the tubes fan out beneath the lower part of the front bank of boiler tubes to a much wider spacing forming a slag screen to protect the boiler tubes and the upper part of the furnace tubes. Near the level of the lower header of the boiler, the furnace tubes divide into two banks, a front bank going to a lower front header and a rear bank going to a lower rear header. Burning material from the firing equipment of the apparatus enters the furnace between the lower headers of the furnace and after passing through the furnace and boiler exits through an opening in the back of the boiler connecting the flue.

Since the furnace extends from an upper header near the level of the upper boiler header to a pair of lower headers below the level of the lower boiler header, its height is greater than that of the boiler. Therefore the furnace, or each unit thereof, is transported on its side with its operating height occupying the axial or Z direction of the right of way. The depth of the furnace, or each unit thereof, may be positioned for travel to correspond to the X or Y direction of the right of way, with the width of the furnace, or each unit thereof, occupying the other X or Y direction. Since the boiler width corresponds to the maximum Z dimension of the right of way, if the furnace is to be as wide or wider than the boiler, the furnace is divided into a plurality of units to be positioned side by side and assembled at point of use. As many furnace units as desired may be used in order to properly utilize the fuel firing equipment needed for the apparatus.

An unfired pressure vessel is disposed outside the boiler and furnace at a level above the upper headers of the boiler and furnace and is connected to these headers by risers. This vessel serves as a steam drum where water separates from steam produced in the furnace and boiler and where steam accumulates. The steam drum is connected by downcomers to the lower headers of the boiler and furnace. There is thus provided a path for thermosiphonic circulation of fluid,

water in the furnace and boiler tubes being converted to steam which rises to the upper headers and thence through the risers to the steam drum where entrapped water separates and falls back through the downcomers to the lower headers.

Additional thermosiphonic circulation is provided directly between the upper and lower headers of the furnace and boiler. Water from the upper header of the furnace is fed to the lower front header by dog leg downcomer tubes imbedded in refractory material to form the front wall of the furnace. Water from the upper header of the boiler is fed to the lower header by dog leg. downcomer tubes imbedded in refractory material to form the rear wall of the boiler. However I this circulation is primarily to effect cooling of the front and rear walls of the steam generating apparatus.

There is a rectangular cross section inner space in the boiler between the rearmost row of the front bank of dog leg tubes and the foremost row of the rear bank of dog leg tubes: Thisspace is occupied by a group of forced-circulation, return-bend tubes for pre-heating the feed water-supplied to the apparatus, such tubes being connected to a lower manifold fed by a pump and discharging into an upper manifold. Water is supplied to the steam drum from the upper manifold of the preheater.

BRIEF DESCRIPTION OF THE DRAWINGS For a detaileddescription of a preferred embodiment of the invention reference will now be made to the accompanying drawings wherein:

' FIGS. 1 and 2 are vertical sections through an apparatus embodying the invention showing respectively furnace and boiler units of the. apparatus;

FIGS. 3, 4, and 5, are sections taken at planes 3-3, 4-4, and 5-5 of FIGS. I and 2;

FIG. 6 is a schematic view illustrating the positions of the boiler and furnace units during transportation; and

FIG. 7 is a schematic side elevation illustrating a steam generating apparatus incorporating the furnace and boiler units of FIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Steam Generating Apparatus Referring now to FIGS. 1, 2 and 7, and particularly FIG. 7 for an overall view, there is shown steam generating apparatus embodying the invention including fuel feeding and firing means 30, which is conventional, and is indicated to include a stoker for burning coal, but which could include oil burners or other known equipment for feeding and firing other fuels. Examples of suitable firing and feeding equipment is shown in U. S. Department of the Interior Office of Coal Research OCR Contract No. 14-01-0001-242 Pulsating Ash Discharge Stoker Applied to a 5000 No./h'our coal fired package boiler. Drawing No.

' OCR-SO- Sheet 19 of 26 are shown in the pamphlet of Babcock & Wilcox entitled The B & W Integral- Furnace Boiler, type FF copyright I962 by the Babcock 8r. Wilcox Company, eg on pages 10 and 11 thereof. Suitable fuelfiring and feeding equipment is also shown at page 91 et seq of the special report of August 1958 published by POWER, 330 West 42nd tled Packaged Boilers, published by BROS Incor-' porated, Power Division, 1057 Tenth Avenue S.E.,

Minneapolis 14, Minnesota, (bearing identification number WT-IO 3500 3-57 MP). These three publications also disclose suitable walls for housing the portion of the steam generating apparatus which contains burning fuel or the products of combustion, such as water cooled refractory walls. These publications also disclose suitable auxiliaries to be used with the apparatus as well as the constructional details of tubing, pipes, headers, and other elements, well known in the art, which will not be set forth in detail herein.

To the rear and extending above the fuel feeding and firing means 30 is a furnace 32 comprising one or more radiation units. To the rear of the furnace is a convection unit or boiler 34. The terms radiation" and.convection refer to the primary mode of heat transfer from the burning fuel and products thereof to the heat exchange means, furnace or boiler.

Within the boiler 34 is a preheater 36. a flue or stack 38 is connected to the upper rear of the boiler and an ash hopper 40 is connected to the lower rear of the boiler.

A pump 42 feeds water to the preheater which in turn discharges into unfired pressure vessel steam drum 44.

Furnace Referring now particularly to FIG. 1, the furnace 32 includes an upper header 50, a front lower header 52, and a rear lower header 54 (see FIG. 2). A bank of tubes in transverse rows 55-60 extends downward and forwardly at an angle of about 45 and then fans out into a larger number of transverse rows 61-70 extending downward and at varying inclinations (from vertical at the front row to a 45 inclination at the rear row). The tubes in the rows 61-70 are spread widely enough (see FIG. 3) to prevent slag from bridging thereacross and serve to cool the hot molten slag contained in the burning fuel until it is below the temperature at which it will attach itself to the more closely spaced tubes in the rows 55-60 and in the boiler. The rows of tubes 61-70 thus provide a slag screen.

The tube rows 61-70 part at a level near the top of the fuel firing and feeding means 30, dividing into a front group or bank portion connecting to front lower header 52 and a rear group or bank portion connecting to rear header 54 (see FIG. 2).

Referring to FIG. 3 as well as FIG. 1, tubes disposed in additional transverse rows 80, 81 extend from the upper header 50 to the front lower header 52. Row

is within the refractory front wall 82 of the apparatus that lines metal casing 86. Water flows down the tubes of row 80 to cool the wall. Row 81, which is a continuation of row 55, has the same relatively close spacing of thetubes as exists in the upper part of the bank of fur- Y nace tubes at rows 56-61. The tubes in row 81 will contain fluid (mostly water) flowing upwardly and will shield the refractory wall 82 that lines casing 86.

Referring now to FIGS. 1, 2, 3 and 4, the relatively widely spaced tubes of the four rear groups of rows 67-70 recombine into two rows 91, 93 of closely spaced tubes, the tubes in one row being staggered relative to those in the other row to form a shield protecting-the refractory wall 95 lining the casing 97 at the rear of the furnace.

The furance sides include refractory walls 100, 102 lining metal casing 104, 106. Also, fore and aft rows of water tubes such as 108, 110 lie against walls 100, 102 and additional fore and aft rows of tubes 112, 114

' spaced from the walls 100, 102 provide a shield therefore.

. Thefurnace may, as shown in FIG. 3, be wider than the boiler. In such case, wherethe furnace extends laterally beyond the boiler the next to the rearmost rows of furnace tubes 69' are displaced rearwardly to align with the tubes of row 70 to form a closely spaced row of tubes as at 116 and 118 to protect the refractory walls 120, 122 lining the metal casing 124, 126 at the rear of the furnace.

If the furnace is wider than the boiler, as shown'in FIG. 3, the furnace will be made of a plurality of side by side units. For example, the width of each unit may be the X dimension of the right of way. As shown in FIG. 3, the furnace includes three such units. The headers of the several units are easily connected together, e.g. by welding, as shown at 130, 132 for the upper headers whose position is indicated in phantom lines in FIG. 3, and as shown at 134, 136 for front lower header 52 and 138, 140 for rear lower header 54. Such an assembly involving end to end joinder of headers is much more feasible than would be an in-the-field integration of units employing large. steam separation and accumulation drums. This is an advantage flowing from the use of an unflred pressure vessel for the steam drum, since the latter will be transported as a separate unit from the furnace and-boiler.

Boiler Referring now particularly to FIGS. 2 and 3, the

boiler 34 includes an upper header 151 and a lower header 153 almost directly therebelow, e.g. within of the vertical. Between" the headers is connected a front bank of forwardly protruding dog leg tubes, including rows 161, 162, 163, and a rear bank of rearwardly protruding dog leg tubes 166 is also connected therebetween, including rows 164, 165, 166.

A An additional row 167 of dog leg tubes at the rear of the boiler interconnecting headers 151, 153 serve as water downcomers to cool refractory wall 169 lining the metal casing 171-at the rear of the boiler. AS shown in FIG. 3, the sides of the boiler'are also formed by refractory walls, e.g. 173, 175, lining metal casings, e.g. 177, 179. The lower header 153 of the boiler lies adjacent the refractory beam 181 at the top rear of the furnace. The top of the apparatus includes a metal casing 183 lined with refractory material 185, against which lie the upper headers 50 and 151 of the furnace and boiler. The entire apparatus is thus enclosed in a casing lined with refractory to contain the burning materials.

There is an opening 187 in the top of the back wall of the boiler to which the flue or stack 38 is connected to discharge the'light productsof combustion into the atmosphere. There is anopening 191 in the bottom of the back wall of the boiler which connects to hopper 40. The lower end of the hopper is closed by a door 193 through which solid products of combustion can periodically be removed. To guide the burning material from the furnace through the boiler, a number of baffle plates 195, 197 are disposed in the boiler, plate 195'extending upwardly from the header 153' and baffle-197' extending downwardly from header 151.

' Preheater I Within the rectangular section space inside the boiler, defined between rows 163 and 164 of the boiler tubes, is disposed preheater 36. The preheater includes a plurality of multiple return bend tubes 201 connected at their upper ends to upper manifold 203 and at their lower end to lowe manifold 205. The upper manifold is disposed at the lower edge of baffle plate 197 and a continuation 198 of the baffle means that includes plate 197 extends downwardly from the upper manifold to a level near the upper edge of a baffle plate 195. The lowe manifold is disposed slightly above baffle plate 195. To prevent ash from accumulating between plate 195 and manifold 205 there is provided a wall plate 210 between the upper side of manifold 205 and the part of plate 195 thereabove. The wall plate 210 is covered with refractory material 212. In addition, a plate 214 is provided between the lower part of manifold 205 and the part of plate 195 therebelow. v

The centrifugal pump 42, has an inlet 220 adapted to be connected to a source of water (not shown). The outlet 222 of the pump is connected to manifold 205 by pipes 206. Upper manifold 203 is connected to steam drum 44 (see FIG. 1) by pipes 218 passing through the casing of the apparatus.

Steam Drum The steam drum 44, which is an elongated body of circular cross-section, closed at both ends, is connected to boiler header 151 by a row 220 of riser tubes and is connected to furnace header 50 by a row 221 of riser tubes. Neither of these headers is intended to serve as a separator for water and steam, it being intended that both be full of water except for steam'bubbles passing upwardly therethrough from the boiler and furnace tubes. 0

Water entrained with the steam bubbles separates therefrom in drum 44 and collects in the lower part of the drum along with makeup water from the preheater. This water is fed out at each side through pipes 250, which branches into pipes 252, 254. Pipes 252 branches again into pipes 256 and 258 which connect to the furnace lower headers 52 and 54. Pipes 254 con.- nects to lower headers 153 of the boiler.

Operation In operation, fuel such as coal or gas oroil, is fired and fed by firing and feedingmeans 30 into the furnace 32. After being cooled by the furnace slag screen it rises up through the furnace 32 and the front bank of tubes of boiler 34, passes over baffle plate 195, down through the preheater 36 and up under baffle plate 197, thencethrough the rear bank of tubes of boiler 34, and the light products of combustion go out stack 38, the heavier products falling into hopper 40. Water in the furnace and boiler tubes is converted to steam and rises through headers 50 and 151 and risers 220, 221 into steam drum 44, a suitable steam outlet pipe, not shown, supplies steam from the drum to the operation to be served with steam. Water is supplied to the system through the pump 42, and is heated by the products of combustion in preheater 36, from which it is fed to the steam drum. Water from the drum is then fed to the lower headers of the furnace and boiler for discharge into the furnace and boiler tubes and conversion therein to steam.

Transportation Referring now to FIG. 6, it is seen how the boiler and furnace units are to be transported. The width of the boiler occupies theZ dimension of the right of way and the height of the boiler occupies a diagonal across the X and Y dimensions of the right of way. The furnace is transported with its height occupying the Z dimension of the right of way and with its headers extending in the direction of the X dimension, its depth occupying the Y dimension. Thus the furnace is allowed to have the maximum height permitted by the right of way. At the same time the boiler -is given the ample height of the diagonal of the X, Y dimensions of the right of way and can be made as wide as the limits of the Z dimension to give ample capacity.

The unfired pressure vessel, not shown in FIG. 6, would be transported with its axis in the Z direction. Since the steam drum is not subjected to the stresses produced by the high temperature of the burning fuel, a great increase in its safety factor is achieved.

While a preferred embodiment of the invention has been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit of the invention.

lclaim:

1. Steam generating apparatus comprising steam separation and storage means including an unfired pressure .vessel and heating means for converting water to steam including upper header means connected to said vessel, lower header means connected to said vessel, and tube means interconnecting said header means,

said heating means including a boiler unit comprising an upper header, a lower header, a front bank of forwardly protruding dog leg tubes interconnecting said headers, and a rearbank of rearwardly projecting dog leg tubes, the cross section of said boiler unit having a rectangular perimeter with the diagonal of said rectangular perimeter passing through said headers and being perpendicular to the horizontal plane, said heating means further including a furnace unit comprising an upper header, lower header means, and a bank of-tubes interconnecting said upper header and said lower header means, said lower header means of said furnace unitincluding a front lower header and a rear lower header, said bank .of tubes of the furnace unit including an upper portion overlying the from upper part of the boiler unit and a medial portion where the tubes fan out to greater lateral spacing forming a slag screen for said upper portion and said boiler unit, said lower portion ultimately dividing into a front part connected to said front lower header and a rear part connected to said rear lower header. 2. Apparatus according to claim 1 wherein there is an interior space in said boiler unit between said front and rear banks-of tubes, said apparatus including a preheater and means connecting said preheater to said unfired pressure vessel, said preheater being disposed in said interior space of said boiler.

3. Apparatus according to claim 1 said preheater including upper and lower manifolds and a bank of return bend tubes interconnecting said manifolds, said upper manifold discharging through the connection means to said unfired pressure vessel, said apparatus including a water pump connected to said lower manifold to effect forced flow of water through said preheater.

4. Apparatus according to claim 1 including fuel feeding and tiring means connected thereto delivering burning material to said furnace unit between said lower headers. 

1. Steam generating apparatus comprising steam separation and storage means including an unfired pressure vessel and heating means for converting water to steam including upper header means connected to said vessel, lower header means connected to said vessel, and tube means interconnecting said header means, said heating means including a boiler unit comprising an upper header, a lower header, a front bank of forwardly protruding dog leg tubes interconnecting said headers, and a rear bank of rearwardly projecting dog leg tubes, the cross section of said boiler unit having a rectangular perimeter with the diagonal of said rectangular perimeter passing through said headers and being perpendicular to the horizontal plane, said heating means further including a furnace unit comprising an upper header, lower header means, and a bank of tubes interconnecting said upper header and said lower header Means, said lower header means of said furnace unit including a front lower header and a rear lower header, said bank of tubes of the furnace unit including an upper portion overlying the front upper part of the boiler unit and a medial portion where the tubes fan out to greater lateral spacing forming a slag screen for said upper portion and said boiler unit, said lower portion ultimately dividing into a front part connected to said front lower header and a rear part connected to said rear lower header.
 2. Apparatus according to claim 1 wherein there is an interior space in said boiler unit between said front and rear banks of tubes, said apparatus including a preheater and means connecting said preheater to said unfired pressure vessel, said preheater being disposed in said interior space of said boiler.
 3. Apparatus according to claim 1 said preheater including upper and lower manifolds and a bank of return bend tubes interconnecting said manifolds, said upper manifold discharging through the connection means to said unfired pressure vessel, said apparatus including a water pump connected to said lower manifold to effect forced flow of water through said preheater.
 4. Apparatus according to claim 1 including fuel feeding and firing means connected thereto delivering burning material to said furnace unit between said lower headers. 